   /*
        * Copyright 1995-1997 Sun Microsystems, Inc.  All Rights Reserved.
        * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
        *
        * This code is free software; you can redistribute it and/or modify it
        * under the terms of the GNU General Public License version 2 only, as
        * published by the Free Software Foundation.  Sun designates this
        * particular file as subject to the "Classpath" exception as provided
        * by Sun in the LICENSE file that accompanied this code.
        *
        * This code is distributed in the hope that it will be useful, but WITHOUT
        * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
        * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
        * version 2 for more details (a copy is included in the LICENSE file that
        * accompanied this code).
        *
        * You should have received a copy of the GNU General Public License version
        * 2 along with this work; if not, write to the Free Software Foundation,
        * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
        *
        * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
        * CA 95054 USA or visit www.sun.com if you need additional information or
        * have any questions.
        */
      package sun.misc;
      
      import java.io.OutputStream;
      import java.io.InputStream;
      import java.io.PrintStream;
      import java.io.IOException;
      
      /**
       * This class implements a BASE64 Character encoder as specified in RFC1521.
       * This RFC is part of the MIME specification as published by the Internet
       * Engineering Task Force (IETF). Unlike some other encoding schemes there
       * is nothing in this encoding that indicates
       * where a buffer starts or ends.
       *
       * This means that the encoded text will simply start with the first line
       * of encoded text and end with the last line of encoded text.
       *
       * @author      Chuck McManis
       * @see         CharacterEncoder
       * @see         BASE64Decoder
       */
      
      public class BASE64Encoder extends CharacterEncoder {
      
          /** this class encodes three bytes per atom. */
          protected int bytesPerAtom() {
              return (3);
          }
      
          /**
           * this class encodes 57 bytes per line. This results in a maximum
           * of 57/3 * 4 or 76 characters per output line. Not counting the
           * line termination.
           */
          protected int bytesPerLine() {
              return (57);
          }
      
          /** This array maps the characters to their 6 bit values */
          private final static char pem_array[] = {
              //       0   1   2   3   4   5   6   7
                      'A','B','C','D','E','F','G','H', // 0
                      'I','J','K','L','M','N','O','P', // 1
                      'Q','R','S','T','U','V','W','X', // 2
                      'Y','Z','a','b','c','d','e','f', // 3
                      'g','h','i','j','k','l','m','n', // 4
                      'o','p','q','r','s','t','u','v', // 5
                      'w','x','y','z','0','1','2','3', // 6
                      '4','5','6','7','8','9','+','/'  // 7
              };
      
          /**
           * encodeAtom - Take three bytes of input and encode it as 4
           * printable characters. Note that if the length in len is less
           * than three is encodes either one or two '=' signs to indicate
           * padding characters.
           */
          protected void encodeAtom(OutputStream outStream, byte data[], int offset, int len)
              throws IOException {
              byte a, b, c;
      
              if (len == 1) {
                  a = data[offset];
                  b = 0;
                  c = 0;
                  outStream.write(pem_array[(a >>> 2) & 0x3F]);
                  outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
                  outStream.write('=');
                  outStream.write('=');
              } else if (len == 2) {
                  a = data[offset];
                  b = data[offset+1];
                  c = 0;
                  outStream.write(pem_array[(a >>> 2) & 0x3F]);
                  outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
                 outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
                 outStream.write('=');
             } else {
                 a = data[offset];
                 b = data[offset+1];
                 c = data[offset+2];
                 outStream.write(pem_array[(a >>> 2) & 0x3F]);
                 outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
                 outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
                 outStream.write(pem_array[c & 0x3F]);
             }
         }
     }

